The overall hypothesis of this proposal is that obese individuals have impaired parasympathetic activation in response to food ingestion compared with normal weight subjects. However, this proposal is composed of three separate studies, each designed to address a different question raised from an earlier study described in a separate proposal (see "Inhibition of parasympathetic nervous system activity: effect on insulin release). Therefore, each study has a different hypotheses and goal. Study 1 will determine whether administration of a small amount of insulin during the pre-absorptive time period is critical for glucoregulation in glucose tolerant and intolerant obese subjects. b) To determine if endogenous insulin release during the pre-absorptive time period is more effective in glucoregulation than exogenous insulin infusion. Study 2 will determine if the rate of gastric emptying of a mixed nutrient meal is different in obese compared with normal weight subjects and if there are differences in parasympathetic control of gastric emptying in obese subjects. Study 3 will evaluate whether different forms but equicaloric amounts of carbohydrate can differentially effect plasma glucagon levels and the rate of diet-induced thermogenesis in normal weight and obese subjects.